1. Field of the Invention
The present invention relates to an apparatus for producing a sound effect in a vehicle, depending on sound source information, including vehicle driving state information or engine operation information.
2. Description of the Related Art
Heretofore, there have been proposed in the art a sound effect producing apparatus for detecting accelerating or decelerating actions made by a driver, and producing and radiating a sound effect into the vehicle cabin, depending on the acceleration or deceleration of the vehicle, by means of a speaker installed in the vehicle cabin, as disclosed in Japanese Laid-Open Patent Publication No. 54-8027 and U.S. Pat. No. 5,371,802.
According to the disclosed sound effect producing apparatus, when the rotational speed (rotational frequency) of a motor vehicle engine increases in response to an accelerating action made by the driver, a sound effect having a high frequency and a large sound level is generated depending on the increase in the engine rotational speed, wherein the sound effect is radiated from the speaker into the vehicle cabin in order to create a staged sound atmosphere in the vehicle cabin.
However, according to the conventional apparatus, which produces a sound effect depending on the rotational speed of the engine, during declutching, there is no correlation between the increase or decrease of the engine rotational speed and actual acceleration or deceleration of the vehicle. For example, when the clutch is disengaged and the accelerator pedal is pressed during downshifting, the engine rotational speed increases and the sound effect becomes larger, even though the actual speed of the vehicle stays constant or decreases. Such a gap may seem strange to the driver or to a passenger riding in the vehicle.
On the other hand, in some situations, it would be better to produce a large sound effect even when the clutch is disengaged. For example, when the clutch is disengaged but the driver uses a driving technique known as “heel-and-toe”, the driver or passenger would not sense any strangeness when the sound effect is made larger.
Generally, the “heel-and-toe” operation is one type of driving technique that is used during downshifting. As its name suggests, during heel-and-toe operations, a downshift operation is performed by both the right heel of the foot heel as well as the right toe. Such a heel-and-toe operation, for example, may be carried out as follows. In order to negotiate a curve, (a) the driver uses his or her right toe in order to apply the brake before reaching the curve so as to decrease the speed of the vehicle; (b) the driver uses his or her left foot in order to push in the clutch pedal and thereby disengage the clutch; (c) the driver uses his or her right heel in order to push the accelerator pedal so that the engine rotational speed stays substantially the same as the wheel rotational speed, while the driver then returns the clutch pedal in order to reengage the clutch to perform downshifting; and (d) the driver pushes the accelerator pedal in order to accelerate the vehicle. According to the above operations, the vehicle is decelerated before reaching the curve and downshifting is performed smoothly. Then, the vehicle is re-accelerated to pass through the curve smoothly and quickly.
During the above operation (c), the engine rotational speed increases while the clutch is disengaged. Therefore, there is no correlation between engine rotational speed and actual acceleration of the vehicle. However, when the heel-and-toe operation is performed, the above operations are performed only for a very short period of time, e.g., for 1 to 2 seconds. Accordingly, the driver or passenger does not experience a strange feeling as a result of the sound effect becoming larger when the engine rotational speed is increased.
Such a situation, where it is better to increase the sound effect during a heel-and-toe operation, can apply not only to cases of using the apparatus for producing a sound effect depending on engine rotational speed, but also to cases of using an apparatus for producing a sound effect depending, for example, on the velocity of the vehicle. In such an apparatus, the sound effect ordinarily will not be increased even when the accelerator pedal is pressed, since the vehicle is decelerated during downshifting using the heel-and-toe operation. However, in order to highlight the heel-and-toe operation, actually it would still be better to increase the sound effect.